Knowledge！The three most common systems of central air conditioning

Posted on 2025-01-08

The first type: water cooling machine

The water-cooled unit belongs to the refrigeration unit part of the central air-conditioning system. Its refrigerant is water, which is called a chiller. The cooling of the condenser is achieved by heat exchange and cooling of normal temperature water.

1. Working form: The outdoor unit is generally called the chiller room in the machine room, and the indoor unit is generally called a fan coil, which is connected by water pipes. (The outdoor unit compresses the refrigerant, and the refrigerant then exchanges heat with water to produce cold water. The cold water is pumped into each indoor unit, and the indoor air and water exchange heat to achieve the purpose of temperature regulation.); Water brings the heat taken out from the room to the outdoor unit, and the outdoor unit sends the heat to the cooling tower through the water system between the outdoor unit and the cooling tower to the external environment.

2. Advantages:

1) High energy consumption ratio, 30% higher than the previous type;

2) The temperature of each room can be adjusted freely; 3) The water pipe takes up less space and is easy to decorate.

3. Disadvantages:

1) The system is complex, more expensive than the previous one, and the construction quality is not high, there is a risk of water leakage, and maintenance is troublesome;

2) Affected by the climate, it cannot work normally when it is below -5℃, and an auxiliary heating device needs to be installed, which also consumes some electricity.

3) The heat exchange efficiency is low and the energy saving is average. As time goes by, the operating cost increases, and professional personnel are required to start, maintain and maintain it, which will incur some costs, and the later costs are high.

The second type: air cooling machine

1. Working mode: The outdoor unit is called an air-cooled heat pump unit. The unit can be arranged on the roof or the ground. The indoor unit is generally called a fan coil unit and is connected by a water pipe. (The outdoor unit compresses the refrigerant, and the refrigerant then exchanges heat with water to produce cold/hot water. The cold/hot water is pumped into each indoor unit by a water pump, and the indoor air exchanges heat with water to achieve the purpose of temperature regulation.) Water brings the cold/heat brought out from the room to the outdoor unit, and the outdoor unit directly discharges the cold/heat to the outside environment through its own fan, eliminating the water system between the cooling tower and the outdoor unit. It is generally suitable for places with a building area of less than 5000m2.

2. Advantages:

1) The module does not occupy the machine room and can be placed on the roof or in a well-ventilated place;

2) Convenient control and independent use, no professional operation is required;

3) Each module has two compressors, which can automatically open the required number of compressors according to the terminal usage, which plays a good energy-saving role;

4) The machine room area is small, and the roof does not occupy the valuable machine room;

5) No boiler or plate heat exchanger is required.

6) The system is simple, the cost is the lowest among the three types, and it is easy to maintain.

3. Disadvantages:

1) Low energy efficiency ratio (relatively speaking), COP is only about 2.9;

2) The actual energy of cooling and heating is greatly affected by the external ambient temperature;

3) When the external temperature is below -9℃, the heating efficiency decays quickly and auxiliary electric heating is required. At present, some products are equipped with auxiliary heating devices to ensure that the outdoor unit can still work at -15℃ or even -20℃, but some additional electricity is required. For example, the American Luther air conditioner can work normally at -18℃.

4) The investment is higher than that of the screw machine, but it is also related to the brand.

5) The air duct occupies a lot of space, about 100×200 square millimeters, and it is necessary to use decoration techniques to reduce its interference with the space;

The third type: VRV system (multi-link)

It is the abbreviation of variable refrigerant volume system, that is, variable refrigerant flow system. It is in the form of a group of outdoor units, which are composed of functional machines, constant speed machines, and variable frequency machines. By connecting the outdoor unit system in parallel, the refrigeration pipes are concentrated into a pipe system, which can be conveniently selected according to the capacity of the indoor unit, and the appropriate capacity of the indoor unit can be selected from 122.5KW in 1.5KW steps, that is, a maximum of 30 indoor units can be connected to one group of outdoor units. Indoor units are ceiling embedded, wall-mounted, floor-standing, etc. Indoor units of different types can be connected to a refrigeration circuit and can be controlled separately. The minimum capacity of the indoor unit is 0.6KW and the maximum is 3.75KW. The capacity of the indoor unit can be adjusted within 50% to 130% of the capacity of the outdoor unit.

1.Working mode: The outdoor unit is connected to multiple indoor units through refrigerant pipes (usually copper pipes), and the indoor units in each room are directly heat exchanged between refrigerant and air. (The outdoor unit compresses the refrigerant, and then the refrigerant is transported to the indoor unit through the copper pipe, where the refrigerant exchanges heat with the indoor air)

2. Advantages:

1)The comfortable temperature fluctuation is small. The indoor temperature fluctuation error can be controlled within the range of ±0.5℃ by using the DSP high-speed chip, avoiding the feeling of hot and cold in ordinary air conditioners, and bringing constant temperature comfort.

2)Each room can be controlled individually, the control is precise, and electricity bills are saved. When only one indoor unit in the system is turned on, the outdoor compressor can adjust the speed or unload accordingly, and reasonably output the energy required by the indoor unit, thereby avoiding the unnecessary energy waste of the traditional central air conditioner "once turned on and fully turned on". Moreover, the indoor and outdoor units of the multi-connected system air conditioner are equipped with computer boards, which can be controlled individually or in partitions. The outdoor unit of the air conditioner can accurately adjust the energy output quickly according to the load changes in the indoor room to avoid waste.

3)High heat exchange efficiency and good energy saving Because the system adopts direct evaporative cooling, the heat exchange process is more direct and the energy loss is minimal. The chiller uses water as the refrigerant. The cold capacity is transferred from the refrigerant to the water, and then the water is sent to the indoor cooling. There are two heat exchanges in this process, which consumes a lot of energy.

4) No hidden danger of water leakage. All copper pipes are connected, and there is no water. It can work normally at -15℃.

2.Disadvantages:

1)High initial investment

2)Since the refrigerant is directly transported to the indoor unit of the air conditioner, once the refrigerant leaks, it is not easy to detect the leak, so the installation requirements of the refrigerant pipe are extremely high.

3) Compared with the cold/hot water system and the duct system, there are requirements for the distance and position difference between the indoor unit of the air conditioner and the outdoor host.